1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive for storing a test pattern in calibration sectors that are longer than user data sectors for zone parameter calibration.
2. Description of the Prior Art
The zone parameters of a disk drive are typically calibrated during manufacturing and stored in a reserved track on the disk. During spin up, the calibrated parameters are read from the reserved track, stored in volatile semiconductor memory, and used to program the disk drive relative to the radial position of head during read and write operations. The prior art has suggested to recalibrate the zone parameters periodically throughout the life of the disk drive to compensate for changes that occur over time. The calibration procedure involves reading a test pattern from the disk and tuning components of the disk drive in response to reading the test pattern. For example, a read channel component may be tuned so as to minimize a mean-square-error between the samples of an ideal read signal and the read signal generated by reading the test pattern. The test pattern is stored in the data sectors of a reserved track in each zone. However because the data sectors are fixed in length, gaps exist between the data sectors resulting in corresponding gaps while reading the test pattern.
There is, therefore, the need for an improved technique for recalibrating the zone parameters of a disk drive in the field to compensate for changes that occur over time due, for example, to changes in environmental conditions.
The present invention may be regarded as a disk drive comprising a disk having a plurality of tracks including a plurality of data tracks and a plurality of reserved tracks, and a plurality of embedded servo sectors dispersed circumferentially around the tracks. The tracks are banded together to form a plurality of zones, each data track comprises a plurality of data sectors each comprising a first number of bits for storing user data, and each reserved track comprises calibration sectors each comprising a second number of bits for storing a calibration test pattern, wherein the second number of bits is greater than the first number of bits. The disk drive further comprises a head actuated radially over the disk for writing data to and reading data from the data sectors, and for reading the calibration test pattern from the calibration sectors. The disk drive employs a plurality of zone parameters used to program the disk drive to read user data from a data sector located in a selected one of the plurality of zones. A disk controller calibrates the zone parameters by executing a calibration procedure, wherein the calibration procedure reads the calibration test pattern from at least one of the calibration sectors.
In one embodiment the calibration sectors extend substantially from one servo sector to the next servo sector. In another embodiment, each calibration sector comprises a preamble and sync mark.
The present invention may also be regarded as a method of calibrating a zone parameter of a disk drive in the field. The disk drive comprises a disk comprising a plurality of tracks including a plurality of data tracks and a plurality of reserved tracks, and a plurality of embedded servo sectors dispersed circumferentially around the tracks. The tracks are banded together to form a plurality of zones, each data track comprises a plurality of data sectors each having a first number of bits for storing user data, and each reserved track comprises calibration sectors each having a second number of bits, wherein the second number of bits is greater than the first number of bits. The method comprises the steps of actuating a head radially over the disk for writing data to and reading data from the data sectors, and for reading the calibration test pattern from the calibration sectors. The zone parameter is calibrated by executing a calibration procedure, wherein the calibration procedure reads the calibration test pattern from at least one of the calibration sectors.